The following abbreviations are herewith defined, at least some of which are referred to within the following description of the state-of-the-art and the present invention.
CPE Customer Premises Equipment
IEEE Institute of Electrical and Electronics Engineers
ITU International Telecommunication Union
MAC Media Access Control
OAM Operation, Administration and Maintenance
PON Passive Optical Network
RAM Random Access Memory
SRAM Static RAM
TDM Time Division Multiplexing
One way of increasing the efficiency of data transmission is to bit-interleave traffic. In one bit-interleaved solution, a transmitter sends data frames that include a synch portion, a header portion, and a payload portions. A node receiving the frame may process (only) one or more lanes of the frame. A lane is defined by a rate, meaning every nth bit of the received frame, or portion thereof, and offset—the position of the first bit in that lane. This means that the processing of each lane, once extracted, may be done at slower and often much slower rate than the rate at which the frame was transmitted.
The synch and header portions of the received frame allow the receiver to determine where the frame begins and glean information about where in the payload a given lane or lanes of traffic are located.
The synch and header portions normally have static lanes, that is, the rate and offset do not vary. The payload may have lanes of varying size because a map in the header portion indicates the rate and offset of a given lane within the payload. Lanes that occupy a greater portion of the payload than others are associated with a higher rate.
Bit-interleaving may be beneficial in a number of environments. One is in a system where a transmitting node sends the same data stream to a number of receiving nodes even though the data stream includes data that is meant for only one (or less than all) of the nodes. The recipient node then processes the data stream and uses only the data that was intended for it, discarding the rest. Bit-interleaving allows each receiver to first extract only that data that is intended for it (one or more lanes) before the bulk of the processing is performed. The useful data may then be processed at a much lower rate.
In another environment, a receiver may be the intended recipient of the entire data frame, but is able to separate it into a number of lanes for individual processing by separate circuits, allowing it to control the rate of processing.
In yet another environment, bit-interleaving lanes may be created to allow a receiving node to simply forward certain lanes of data on certain egress ports, perhaps combining it with data lanes from another source but also for forwarding on the respective ports. The packets may have to be processed by the next node or nodes, but not by the “zombie” node that is simply forwarding.
Although the bit-interleaved frames gaining these advantages may be relatively easily mapped, performing the actual interleaving required may be more of a challenge to the point of making it impracticable. The present invention addresses this challenge.
Note that the techniques or schemes described herein as existing, possible, or desirable are presented as background for the present invention, but no admission is made thereby that these techniques and schemes or the need for them were heretofore commercialized or known to others besides the inventors.